A year or two ago my eye was caught by the cover of a magazine on an American news-stand. It was a magazine for the working woman, and its title, in the best traditions of the me-generation, was Self. The cover advertised articles with titles like ‘The Problems of the Kept Man’ and ‘What if He Says No?’ But what attracted my attention was the rather Californian injunction flashed in bold letters across the top: ‘Let’s Be Real!’

Of such stirring raw material is philosophical reflection made. But it can be difficult for philosophers to persuade others that worrying about such hardy perennials as realism and idealism is any more than neurotic. It is often difficult for them even to show their colleagues where the nub of the problem lies. Sir Karl Popper, who was 80 in 1982, is probably the philosopher outstandingly associated in the public mind with showing that such disputes do matter, that the enterprise of science, which aims to discover the truth about the universe we live in, is continually under threat from quacks and the pedlars of false certainty. He has shown that what satisfies our curiosity may not be true. His attacks on Marxism, astrology and psychoanalysis have been widely influential. Many working scientists testify to the effect he has had on the actual practice of their art. And although there is a suspicion of redundancy about the title In Pursuit of Truth on a philosopher’s festschrift (rather as though one discovered the title Against Sin on a festschrift for the Pope), it is Popper above all who is associated with demonstrating that if we care about knowing the truth, it matters very much how we set about it.

A Pocket Popper (no hyphen) is a selection of 30 readings from his work, in four sections on epistemology, the philosophy of science, metaphysics and social philosophy. The selection admirably shows the breadth of Popper’s concerns, and the reason it is a deeply unsatisfactory book is no reflection on the job the editor has done. It is that Popper is particularly badly misrepresented by being carved into bite-size chunks. The book gives one the unfair impression of Popper as moving briskly down an agenda of problems, ticking them off as he solves them in a mere five or six pages apiece. This not only tends to obscure the links between the different areas of his thought: it gives a taste of the energy of his argumentative style but barely a hint of its subtlety. Since Popper’s public reputation is as something of a blunderbuss, some of whose arguments devastate their target while others miss by many yards, this impression is an unfortunate one.

Any reader new to Popper who notes the confident, almost dismissive tones of the extract in which he ‘solves’ Hume’s problem of induction in a page and a half would be unlikely to guess that Popper thinks induction so difficult and complex a problem that he returns to it again and again in the main body of The Logic of Scientific Discovery and in the first volume of the Postscript under review here. Die Logik der Forschung was published in 1934 but was not translated into English until 1959. The Postscript has been circulated like samizdat since 1957 but is only now available in published form. Of its three volumes, the second has been discussed in these columns already (Vol. 5, No 15), while the third is on quantum physics.

The first volume, Realism and the Aim of Science, is the most directly continuous with the original work. Like the original, it is concerned with what Popper sees as the two central problems of the theory of knowledge: namely, the problem of induction and the problem of demarcation (of what distinguishes science from non-science). Underlying both of these is the problem of reconciling our sense that there exists a world independent of our theories about it, with the sceptical doubts of Hume concerning our justification for drawing general conclusions about the world on the basis of particular and finite observations. Many philosophers have resolved the tension simply by declaring that Hume was wrong, that the fact that we cannot make a deductively valid inference from the particular to the general does not mean we cannot make an inductively valid one. That, it is said, is what the ‘logic of inference’ is all about.

Popper’s claim – and if true, it is a remarkable one – is to have solved the problem of induction while accepting that in the essentials Hume was right, and that therefore we are not justified in reasoning from individual instances to general laws. Thus no number of observations of white swans can justify our assertion that all swans everywhere are white. They cannot even make it probable, he insists, that all swans everywhere are white. There is only one way of reasoning from the general to the particular, and that is by falsification, not verification. A single instance of a black swan does justify our assertion that it is false that all swans are white. Science proceeds not by trying to justify true theories but by seeking to eliminate false ones. What is distinctive about science, then – and this is where demarcation comes in – is that it makes possible the pursuit, and thus the elimination, of falsehood. Justification, and with it subjective certainty, are chimerical: if you care more about certainty than about truth you will never go beyond what the observations warrant, so you will go nowhere. It matters not a jot how our theories are reached: we may dream them, invent them as a joke or discern them in the tea-leaves. What does matter is the criticism to which we subject them, and the possibility of rejecting them as false. If there is no such possibility, these theories are no part of the enterprise of science. For Popper – unlike the logical positivists – this does not make them nonsense: they may be respectable metaphysics (like the principle of causality), or meaningful but bogus (like astrology).

Letters

In Pursuit of Truth: Essays in Honour of Karl Popper’s 80th Birthday, edited by Paul Levinson, and reviewed by Paul Seabright in the last issue, is no longer being published in this country by Harvester Press. Copies are available from Humanities Press, Atlantic Highlands, New Jersey 07716.